I need to take photos of some factories. I tried with flash on and off on my Fuji 30i mini camera. Both results are unsatisfactory. The first one is the background is too dark - insufficient flash power I believe. The second one is bright but not sharp - I guess the shutter speed is too long. I cannot carry a powerful flash or tripod due to inconvenient to my job. Any idea I can improve the photo quality.

Have you tried a Brightness and Contrast adjustment on the first photo? Using a Photo Editing program like Paint Shop Pro, Photoshop, or PhotoImpact can do great things for dark pictures. Also some printer and camera software has correction features as part of the package. Give it a try.

Take a look at the EXIF data for the photo that was bright, but not sharp. Make sure the aperature was at the largest possible for your camera (smallest f/stop value).

Next, look at the shutter speed. Likely the "blurriness" is due to shake (any unintentiional camera motion while the shutter is open). If you brace yourself against a post, wall, ... you can manage much longer exposure time. Do some practicing near your computer so you can quickly download the picture and look at the details for sharpness. You will quickly figure out what the longest shutter speed you can use.

Keep in mind that the longest shutter speed depends on the focal length used. You will need a shorter time for longer lengths.